Electronic mail (e-mail) systems have traditionally permitted users to exchange arbitrary text messages. However, e-mail systems have evolved to enable the exchange of a richer variety of content. For example, using the Multi-purpose Internet Messaging Extensions (MIME) format, an e-mail message may be divided into multiple sections, each associated with a different content type. For example, one part of the message may be encoded as "text/plain" and contain a standard text message of arbitrary length, while another part may be encoded as "base64" (a way of encoding binary data in a text form) and contain a wordprocessor document, while yet another part may be a "base64" encoding of a LOTUS 123 (Trademark of Lotus Corp.) spreadsheet. In general, therefore, an e-mail message may contain many sub-documents or attachments. To view each part of the e-mail, the e-mail program may need to invoke a different viewer application. An e-mail message may contain many parts, and each part may contain multiple pages of complex layout and graphics.
Recently, there has also been a proliferation of small devices for use by mobile professionals. These devices, for example, cellular phones, two-way pagers, and palm-top computers, are being enabled to support the delivery of electronic mail. For example, the LOTUS PAGER GATEWAY (Trademark of Lotus Corp.) receives electronic mail messages and generates pages containing information on the message sender, subject, and a summary of its textual content. Moreover, the user, upon receiving a page, can initiate an e-mail reply by sending a pager message back to the Pager Gateway. Similar mechanisms are being provided to deliver e-mail (either in the form of textual data or in the form of a voice phone call) to cellular phones.
However, it is impractical to deliver e-mail attachments (i.e. non-textual documents or even long textual documents) to these mobile devices. First, mobile devices are characterized by limited display capabilities. For example, a two-way pager may only be able to display 3-4 lines of alphanumeric text. These devices are generally incapable of displaying large content, and they are certainly incapable of doing so in a manner that preserves the layout and content of the original application. Moreover, the devices have limited memory. They do not have the capacity to store or execute multiple viewer applications to support the potential range of e-mail attachment types. Finally, network bandwidth to these devices is typically quite limited making it is impractical and/or expensive to deliver large attachments to the device.
Existing e-mail systems that deliver messages to client devices simply discard attachments, possibly saving them for later retrieval by the user when he accesses the mail via a desktop or laptop machine over a network having acceptable bandwidth capacity. This approach has the undesirable effect of preventing the mobile user from accessing or manipulating the attachment when he first learns of the e-mail on the mobile device.
Therefore, a need exists for a method and system that allows mobile users to access e-mail attachments from a low-capability device. The user should be able to delete the attachments from the server memory and also be able to remotely invoke the viewing application, control its behavior, and direct its output. For example, he should be able to direct the output to a local printer, initiate its transmission by fax, or initiate a screen reader program to deliver the message over a voice telephone call.